Double acting contact spring



NOV. 17, 1970 r p. WILSON ET AL I 3,541,287

DOUBLE ACTING CONTACT SPRING Filed Sept', 24, 1968 2 Sheets-Sheet 1 i A i NOV. 17., 1970 P w so ETAL 3,541,287

DOUBLE ACTING CONTACT SPRING Filed Sept. 24, 1968 2 Sheets-Sheet 2 1/ V /I///////////// f// l// j/l/A 'EL ""37 32 an 5 vZmwam I 9 W W United States Patent Office 3,541,287 DOUBLE ACTING CONTACT SPRING Peter Wilson, Gayton, Wirral, and James Aidan Milner,

Huyton, England, assignors, by mesne assignments, to

-BICC-Burndy, St. Helens, Lancashire, England Filed Sept. 24, 1968, Ser. No. 762,080

- Int. Cl. H01n 1/10 U.S. Cl, 200-166 9 Claims ABSTRACT OF THE DISCLOSURE 'An electrical contact element for use in establishing electrical connections by sliding engagement with mating electrical conductors such as printed circuits. The contact element includes a reversely bent cantilever arm 'which can be attached at one end to a connector body, and a second cantilever arm which is attached at one end to the free end of the reversely bent arm. The second cantilever arm serves as the principal electrical path to a mating conductor, while the reversely bent arm engages the conductor, or the conductor support, mainly for the purpose of positioning the second arm properly relative to the conductor.

In general this invention relates to resilient electrical contacts which establish electrical connections by sliding into engagement with a mating electrical conductor. More specifically, this invention relates to electrical contacts which can be mounted to a connector housing so as to engage mating conductors with consistent contact pressure independently of relative displacement of the contact within a given range.

The electrical contacts of this invention have particular application to connectors designed for receiving a plurality of aligned conductors such as may be arranged at the edge of a printed circuit board. Contact elements having resilient compression characteristics for printed circuits and other sliding engagement applications have been disclosed in the' prior art. In the prior art, contact pressure between a contact element and a mating conductor generally varies considerably depending upon variations in the dimensions and alignment of the conductor relative to the contact and its support or housing.

It is an object of this lIllVGHtlOll to provide a resilient electric contact which can engage a mating conductor with limited, predetermined pressure, substantially independently of the relationship between the size or alignment of the conductor and the contact mounting.

Another object of this invention is the provision of a resilient electric contact which minimizes the possibility that excessive pressure or scraping will damage a mating conductor.

Still other objects of this invention include: providing an electric contact which is simple and inexpensive to manufacture; providing a contact element which is adaptable to existing electrical connector housing structures; and providing a contact element which is reliable and effective in operation.

These, and other objects, features, and advantages of this invention will be more particularly pointed out, distinctly claimed, and clearly illustrated in the following specification, claims, and drawings, in which:

FIG. 1 is a side elevation view of a first embodiment of a resilient contact engaging a printed circuit board drawn to an enlarged scale;

FIG. 2 is a sectional view taken on the line II-II in FIG. 1;

FIG. 3 is a plan view of the resilient contact with the printed circuit board omitted;

FIG. 4 is a side elevation view of a second embodiment 3,541,287 Patented Nov. 17, 1970 of a resilient contact engaging a printed circuit board drawn to an enlarged scale;

FIG. 5 is an end view of the resilient contact and printed circuit board shown in FIG. 4, and

FIG. 6 is a plan view of the resilient contact with the printed circuit board omitted.

The resilient electric contact shown in FIGS. 1 to 3 comprises a unitary resilient metal strip 1, bent transversely to its longitudinal axis into the general shape of a U. In use, the strip is mounted at one end to a body or housing 4 as shown in FIG. 1.

The bight of the U 3, forms a resilient root or base for the cantilever arm 2 which is defined by the remaining end of the strip 1. Cantilever arm 2 is shaped to provide two spaced-apart outwardly curved humps 6 and 7.

At the free end of arm 2, adjacent to hump 7, the center of the strip is longitudinally recessed, as at 8. In use, recess 8 assures that the pair. of outer marginal tracks 9 of the strip will engage a mating conductor such as printed circuit board 5 (shown in FIG. 1.)

Between the humps 6 and 7 a U-shaped opening 10 is cut into strip 1, so as to form integral central cantilever arm 11. The resulting arm is coupled at one end to the free end of cantilever arm 2. This second cantilever arm 11 is curved outwardly away from the first cantilever arm '2 to define a contact surface 12 which is adapted to bear against a mating conductor such as printed circuit board 5. Further, cantilever arm 11 preferably is tapered from its base or root end toward its free end, and is of such width that it makes contact only with that part of a mating conductor or support which is not engaged by marginal tracks 9.

The second hump, 6, on cantilever arm 2, serves as a third point of engagement between the contact element and the mating conductor and conductor supports.

The embodiment of this invention illustrated in FIGS. 4 to 6 is formed from a length of resilient wire bent into the general shape of a U, with two humps 26 and 27 formed on the cantilever arm portion 22. In this embodiment, however, the second cantilever arm 31 is formed by an integral extension of the wire, bent back from the free end of the arm 22 in a plane parallel to and spaced from the plane defined by the U. A curved hump portion 32 is formed near the free end of the second arm 31, to provide a third point of engagement between this contact element and a mating conductor such as printed circuit board 25.

Contact elements constructed in accordance with this invention are suitable for use in conventional printed circuit connector housings, where they may be mounted conveniently in standard, side-by-side relationship. They are suitable, similarly, for mounting in opposed pairs to make contact with opposite sides of a mating conductor or conductors.

Although simple, U-shaped elements have been illustrated, it is clear that the invention is applicable equally to other forms, such as the so-called bellows contacts, in which a plurality of bends are provided in zig-zag manner to achieve greater resilience.

The contact elements of this invention will accommodate readily, tolerance variations in the connector bodies, contacts, and conductors, without substantially affecting contact pressure. As a result of this ability of the contact elements, the effects of relative distortion and warping of a printed circuit board will be minimized to help maintain electrical continuity in multi-contact connectors.

In connectors using prior art contact elements, it is necessary frequently to accept contact loading forces of, say, 10 to 12 ounces in order to assure desired minimum contact pressure. Repeated removal and replacement of conductor circuit boards under such conditions frequently damages fragile conductors and conductor coatings. On the other hand, the double-acting contact elements of this invention can be dimensioned to provide substantially constant minimum load and pressure within a reasonably wide range of dimensional and displacement values.

The invention has thus been described but it is desired to be understood that it is not confined to the particular forms or usages shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of the invention; therefore, the right is broadly claimed to employ all equivalent instrumentalities coming within the scope of the appended claims, and by means of which objects of this invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to obtain these objects and accomplish these results.

We claim:

1. A resilient electric contact element for engaging a substantially planar mating electric conductor device, comprising:

a first resilient cantilever arm having a free end and a support end and at least one engaging surface; a second resilient cantilever arm having a free end and a support end and at least one engaging surface;

the support end of said second cantilever arm being coupled to the free end of said first cantilever arm with the free end of said second cantilever arm extending in the direction of the support end of said first cantilever arm;

the said engaging surface on said first cantilever arm being positioned relative to the said free end of said first cantilever arm in a predetermined relationship adapted to position the support end of the second cantilever arm in a given attitude relative to the plane of a substantially planar mating electric conductor device, upon engagement between said engaging surfaces and the mating electric conductor device.

2. A resilient electric contact element in accordance with claim 1 wherein said first cantilever arm is provided with at least two longitudinally spaced-apart contact surfaces, and said second cantilever arm extends in a longitudinal direction from the free end of said first cantilever arm.

3. A resilient electric contact element in accordance with claim 2, wherein the surface area of the engaging surface on said first cantilever arm is greater than the surface area of the engaging surface on said second cantilever arm.

4. A resilient electric contact element in accordance with claim 3, wherein: the engaging surface on said cantilever arm is displaced laterally from the engaging surface on said first cantilever arm relative to the longitudinal direction of said contact element, such that upon engagement of said contact element with a mating electric con- 4 ductor device in the longitudinal direction, the respective engaging surfaces on said first and said second cantilever arms will follow separate paths across said mating electric conductor device.

5. A resilient electric contact element in accordance with claim 2 wherein the engaging surfaces on said first cantilever arm comprise: a first pair of spaced-apart engaging surfaces each of the pair being displaced laterally from the longitudinal direction of said contact element on opposite sides respectively of the longitudinal axis of said second cantilever arm; and a second engaging surface longitudinally spaced from said pair of engaging surfaces.

6. A resilient electric contact element in accordance with claim 5 wherein a centrally disposed longitudinal depressed portion of said first cantilever arm separates said first pair of spaced-apart engaging surfaces from each other.

7. A resilient electric contact element as defined in claim 1 wherein a cross-section of said second cantilever arm considered transversely to the longitudinal direction of said contact element differs from the corresponding cross-section of said first cantilever arm so as to provide said second cantilever arm with a greater degree of resilience than said first cantilever arm.

8. A resilient electric contact element as defined in any one of claims 1 and 6, wherein said first and said second cantilever arms are formed of a single strip of resilient conductive metal bent transversely to the longitudinal axes into the general form of a U, having two arm portions interconnected by a bight portion;

one arm portion of the U and the bight portion forming the said fixed end of said first cantilever arm, and the other arm portion of said U forming the said first cantilever arm;

the said other arm of said U having a pair of longitudinally spaced-apart smoothly curved humps thereon forming the engaging surfaces of said first cantilever arm;

said other arm of said U further including an integral central tongue subportion formed thereof between said longitudinally spaced-apart humps, forming said second cantilever arm;

the said engaging surface of said second cantilever arm being formed on said integral central tongue.

9. A resilient electric contact element as defined in any one of claims 2 and 4, wherein said first cantilever arm and said second cantilever arm comprise an integral structure formed of a unitary length of electrically conductive material.

References Cited UNITED STATES PATENTS 3,152,237 10/1964 Richert et al. 3,324,268 6/1967 Adams. 3,328,540 6/1967 Zoda et al.

HERMAN O. JONES, Primary Examiner 

